Construction of mhd electrical power generator



31 U l l FIPSUZ CONSTRUCTION OF MHD ELECTRICAL POWER GENERATOR FiledDec. 26, 1961 9 SheetsShee 11 l e E yV 6 u l u..

April 26, 1966 E. F. BRILL ETAL 3,248,578

CONSTRUCTION OF MHD ELECTRICAL POWER GENERATOR Filed Dec. 26, 1961 9Sheets-Sheet 2 April 26, 1966 E. F. BRILL ETAL CONSTRUCTION OF MHDELECTRICAL POWER GENERATOR 9 Sheets-Sheet 3 Filed Dec.

Aplll 25, 1966 E. F. BRILL ETAI.

CONSTRUCTION OF MHD ELECTRICAL POWER GENERATOR 9 Sheets-Sheet 4 FiledDeo.

I IIiIIiIlTIV ISI I Ill ILIIzI t IL .IIIIEXIIEIIIIIIEI April 26, 1966 E.F. BRILL ETAL CONSTRUCTION OF MHD ELECTRICAL POWER GENERATOR Filed Deo.26, 1961 9 Sheets-Sheet 5 April 26, 1966 E. F. BRILL ETAL CONSTRUCTIONOF MHD ELECTRICAL POWER GENERATOR 9 Sheets-Sheet G Filed Dec. 26, 1961Aprll 26, 1966 E. F. BRILL ETAL 3,248,578

CONSTRUCTION OF MHD ELECTRICAL POWER GENERATOR Filed Deo. 26, 1961 9Sheets-Sheet 7 fA/Vf 1775/7 E. F` BRILL. ETA.

pril 2G, 1966 CONSTRUCTION OF MHD ELECTRICAL POWER GENERATOR 9Sheets-Sheet 8 Filed Dec. 26, 1961 April 26, 1966 E. F. BRILI. r-:TAL

CONSTRUCTION OF MHD ELECTRICAL POWER GENERATOR 9 Sheets-Sheet 9 FiledDec. 26, 1961 NWN NNN NNW www mwN United States Patent O 3,248,578CONSTRUCTION F MHD ELECTRICAL POWER GENERATR Edward F. Brill,Brookfield, .and Ernst K. Kaeser, West Allis, Wis., assignors toAliisChalmers Manufacturing Company, Milwaukee, Wis.

Filed Dec. 26, 196i, Ser. No. 161,787 8 Claims. (Cl. S10-ll) Thisinvention relates generally to magnetohydrodynamic (MHD) devices. Moreparticularly, it relates to improvements in the construction of MHDdevices such as large scale MHD electrical power generators.

The overall etliciency of convenional steam turbine type plants forgenerating electrical power has gradually been increased over the yearsto the present day value of about 35 to 40 percent. Further increases inthe efficiency of this type of plant will be diflicult to achievebecause of material limitations and increasing initial constructioncosts. To obtain increased power plant efficiency, therefore, newconcepts in electrical power generation must be employed.

The MHD principle of generating electrical power by moving anelectrically conductive fluid, such as a hot ionized gas or plasma,through a magnetic field has been known for some time. Experimentalgenerators employing this principle and capable of generating, forexample, about forty kilowatts of electrical power for short periods oftime have been built and operated. Such generators usually comprise anelongated, heat resistant, electrically insulated flow channel throughwhich the hot ionized gas or plasma is blown, electromagnetic meanssurrounding the flow channel for providing a magnetic field in thechannel, and electrodes inside the channel along two opposite wallsthereof for collecting the current generated in the gas or plasma as itmoves through the magnetic field. Studies show that a properly designedlarge scale MHD electrical generator in a carefully planned system willprovide plant efficiencies of about 50 to 55 percent and afford otherimportant advantages, such as absence of moving and rotating parts,reduced maintenance and simplification of component design.

Heretofore, there have been several drawbacks to the development ofefficient, large scale MHD electrical generators capable of continuouslyproducing commercially significant amounts of electrical power, i.e.,100 megawatts and above.

First of all, for example, such an MHD device is extremely largephysically and is difficult and costly to fabricate by conventionalmethods.

Thermal efficiency poses another problem. Generally speaking, in thermalpower conversion, the larger the device, the more eilicient it is.Similarly, the higher the temperature of the power producing media(steam, gas, plasma, etc.) the higher the eiciency that results. SinceMHD devices primarily comprise stationary components, it is possible touse higher temperature media than is used in conventional complexrotating machinery of comparable size. However, to obtain maximumefficiency it is necessary that the MHD device be designed andconstructed so that heat losses from within the device are reduced to aminimum.

Another serious drawback has been the lack of construction material ableto withstand the extremely high temperatures and high gas velocitiesinvolved in high powered MHD devices, i.e., gas or plasma temperaturesof 5050 or higher and near-sonic velocities in the flow channel andcorrespondingly high temperatures in other parts of the equipment. Nocommercially available materials in themselves are well suited for usein defining the flow channel or acting as insulating or electrode meansin the flow channel in such devices. Most metals,

for example, are not serviceable for any length of time above 2000 F.and thus are not well suited for use as electrodes or as structuralmembers. Similarly, since there is an oxidizing atmosphere in the flowchannel, many materials tend to disintegrate and are not useful asinsulating liners or structural members. Certain materials such asmagnesium oxide, thorium oxide, beryllium oxide and other fully oxidizedmaterials are thermodynamically stable in a high temperature oxidizingatmosphere but tend to become electrically conductive and lose theirvalue as insulation unless this effect can be overcome.

Further problems are posed by attempting to obtain maximum effectivenessfrom the electromagnet employed to provide the magnetic field in theflow channel and in locating the electromagnet to provide maximum fluxdensity in the flow channel.

Then, too, there have been design difficulties encountered in trying tocope with special phenomena peculiar to MHD devices which reduce theefliciency thereof. For example, poor electrical conductivity throughpartially ionized gas in the flow channel accounts for reducedeiliciency. Flux density variation which causes circulating electricalcurrents in the ionized gas -or plasma and short circuiting in such gasor plasma as it enters and leaves the magnetic field result in furthereiciency losses. Poor electron emission from the electrodes into theionized gas and Hall effects account for further internal losses.

Accordingly, it is an object of this invention to provide an improvedhighly efficient large scale MHD device such as an electrical powergenerator for operation at extremely high temperatures which isconstructed of and employs known materials in such a manner as toovercome the high temperature problems outlined above, which largelyovercomes the scientific problems peculiar to MHD devices, and which hasother important advantages.

Another object is to provide an improved large scale MHD device of the:aforesaid character having Ia modular design which permits maximumduplication of components a-nd which facilitates it-s manufacture,assembly, servicing and repair.

Another object is to provide an improved MHD device of the aforesaidcharacter having a flow channel which is defined by improved insulatingmeans and improved electrode means, such means being adapted towithstand extremely high temperatures, to inhibit heat loss from theflow channel and to protect other components of the device from hightemperature damage.

Another object is to provide an improved MHD device of the aforesaidcharacter wherein the electromagnetic means are arranged in such a wayas to obtain minimum reluctance in the magnetic circuit and maximumconcentration of flux in the flow channel.

Other objects and advantages of the invention will hereinafter appear.

A generator constructed in accordance with the present inventioncomprises a hollow steel body portion which is made of a stack ofalternately arranged frame plates and yoke plates which are securedagainst displacement. Each frame plate and yoke plate comprises aplurality of pieces. Each frame plate and yoke plate has an H-shapedhole therethrough and these holes align to provide an axial passagewayhaving an H-shaped cross sectional configuration through the bodyportion. Those portions of the frame plates and yoke plates adjacent theconstricted part of the H-shaped passageway cooperate to define twoelongated magnet poles. Means are provided to secure frame plates andyoke plates together.

The body portion of the generator supports an elongated magnet coil,preferably fluid cooled, which is arranged within the passageway so asto surround the two elongated magnet poles, i.e., one-half of theconductors extend axially through one side of the H-shaped passagewayand the other half extend axially through the other side of the H-shapedpassage-way. For convenience, the coil is preferably fabricated ofsmaller sections.

The body portion of the generator also supports insulating means andelectrode means which are arranged within the passageway and define atapered ow channel of rectangular cross sectional configuration in theconstricted part of the passageway where the magnetic field is densestfor the iiow of high temperature, high Velocity, electrically conductivegases or plasma. Such gases or plasma are supplied to the narrow end ofthe ow channel through a water cooled nozzle by means such as a cyclonefurnace. Preferably, seeding material in the form of potassium compoundsis added to the gases in the nozzle to render the gases fullyconductive.

The aforesaid insulating means take the form of insulating blocks,fabricated of oxidized material, which are disposed along the faces ofthe two elongated poles to define two opposite sides of the flowchannel. Each block has internal passages which communicate with theflow channel *through louvers on the face of the block. Relativelyelectrically nonconductiveI gas, such as pressurized air or flue gas,from a source outside of the generator is supplied to the passages inthe block and flows through the louvers to provide a film of cooling andinsulating gas on the face of the block.

The aforesaid electrode means take the form of individual consumableelectrodes which are arranged in two oppositely disposed double rowsalong the passageway and define the two remaining sides of the owchannel. Each consumbale electrode is made up of electrically conductiveconsumable material in particulate form, such as crushed coal or thelike, which is forced through a tapered electrode chute or box.Preferably, seeding material is mixed with the crushed coal. Eachelectrode chute extends through a radially disposed hole provided in thebody portion of the generator. The inner end portion of each electrodechute extends in front of the conductors comprising the magnet coillying along one side of the H-shape-d passageway and terminates at theside of the ow channel. Means located on the exterior of the bodyportion of thel generator supply crushed coal to the electrode chute andforce it slowly therethrough. Control means are provided to regulate thefeed of the consumable electrodes into the ow channel. Such controlmeans, for example, are responsive to temperature variations within theflow channel to indicate electrode length.

Insulating blocks similar to those above described are disposed in theinterstices between the inner ends of the individual electrodes tocomplete the wall surfaces and to electrically insulate electrodes ofthe same polarity from one another. The passages in the latterinsulating blocks are connected to the passages in the insulating blockshereinbefore described and are supplied with air therefrom.

In addition, heat resistant air supply means for supplying pressurizedair are located along each side of the flow channel behind the inner endponti-ons of the electro de chutes and in front of the conductorscomprising the magnet coil. This pressurized air flowing into the theflow channel tends to keep the gases confined in the flow channel, tocool the electrodes, and is also a source of secondary combustion air.

The electrical connection to each electrode can be made directly to theelectrode chute at a point where the chute leaves the body portion ofthe generator. Or, if preferred, a water cooled conduct-or may beconnected to the electrode chute and led across part of the pole facewithin the passageway behind the associated insulating block; beingbrought out of the generator at another position. This latterarrangement provides' a compensating magnetic eld across the pole faceto cancel the effects of changes in load current on the excitation ofthe generator.

Each pair of opposing electrodes of opposite polarity is adapted forelectrical connection to a load device. Or, if preferred, the electrodesmay be connected to means which convert the D.C. power produced by thegenerator to A.C. power of desired voltage.

The accompanying drawings illustrate a preferred embodiment of theinvention but it is to be understood that the embodiment illustrated issusceptible of modification with respect to certain details thereofwithout departing from the scope of the appended claims.

In the drawings:

FIG. l is an isometric view of the exterior of an MHD electrical powergenerator incorporating the present invention;

FIG. 2 is an exploded view showing the configuration and relationship ofa typical frame member and yoke member which comprise the body portionof the generator shown in FIG. l;

FIG. 3 is a cross sectional View of frame members and yoke members takenalong line III--III in FIG. 2 showing how they are secured together bydoweling;

FIG. -4 is a cross sectional broken view of the generator taken alongline IVIV of FIG. 1 and an elevational view of a cyclone furnaceassociated therewith;

FIG. 5 is a cross sectional broken view of the generator taken alongline V-V of FIG. l;

FIG. 6 is an enlarged cross sectional view of the generator taken alongline VI-VI of FIG. 5;

FIG. 7 is a view of the generator, partly, in section and partly inelevation, taken along staggered line VII- VII of FIG. 6;

FIG. 8 is a view of the generator, partly in section and partly inelevation, taken along the line VIII-VIII of FIG. 5 and showing portionsof electrode means and air intake means on the exterior of the bodyportion of the generator;

FIG. 9 is an isometric view of a portion of the insulating meansemployed in the passageway in the body portion of the generator todefine the flow channel;

FIG. l0 is a diagrammatic view showing the manner in which a set ofelectrodes is electrically connected to a load device through inverters;

FIG. l1 is an enlarged detail view of the interior of the electrodemeans shown in FIG. 8;

FIG. 12 is a side elevational view of the electrode means of the typeshown in FIG. ll and FIG. 13 is a sectional view taken along line XIII-XIII of FIG. l2.

FIG. l shows the exterior of a large MHD electrical power generatorincorporating the present invention. It may be assumed, for example,that the genera-tor is adapted to deliver about 265 megawatts of D C.electrical power at 2000 volts, is about 60 feet high, 22 feet wide and18 feet deep, and weighs about 3500 tons. The generator is constructedof modular components to facilitate its manufacture, assembly andsubsequent servicing. Preferably, the generator is vertically mounted tofacilitate its assembly and to effect economies in the size,arrangement, cost and efficiency of the power plant in which it isincorporated.

The generator body portion The generator comprises a hollow body portion10 which is vertically supported on a base member 12 and is providedwith a cover member 14. Body portion 10, which is fabricated of steel orother magnetizable material, is part of the magnetic circuit of thegenerator and also affords mechanical support for other components ofthe generator which will hereinafter be described.

FIGS. l through 5 show that, in keeping with the Inodular concept ofconstruction, body portion 10 comprises a plurality of frame plates orframe members 16 and a plurality of yoke plates or yoke members 18 whichare alternately stacked in vertical arrangement on base member 12 andwhich are secured together against displacement by attachment meanshereinafter described. Preferably the frame plates 16 are all of thesame thickness and the yoke plates 18 are all of the same thickness butthe yoke plates are substantially thicker than the frame plates.

FIG. 2 discloses a typical frame plate 16 and yoke plate 18. Each frameplate 16 and each yoke plate 18 is provided with an I-I-shaped centrallydisposed aperture 20 and 22, respectively. Thus, when the frame plates16 and 'the yoke plates 18 are stacked, the apertures 20 and 22 thereinalign to define a passageway 24, shown in FIGS. 4 and 5, having anH-shaped cross sectional configuration which extends axially throughbody portion of the generator. It is preferred that passageway 24 betapered and this is accomplished by providing the frame plates 16 andthe yoke plates 18 with apertures 28 and 22, respectively, which differin size. Passageway 24 is adapted to accommodate a lmagnet coil 26,hereinafter described, and to accommodate insulating means and electrodemeans, hereinafter described, which define a flow channel 28, shown inFIGS. l, 4, 5, 6, 7 and 8, for accommodating the flow of hotelectrically conductive gases. As FIG. 2 shows, the apertures 28 and 22in each frame plate 16 and each yoke plate 18, respectively, arecons-tricted near the center thereof and, when the plates are stackedtogether, those portions of the frame plate and the yoke plate whichform such constrictions align to provide elongated, oppositely disposedmagnet poles 30 in body portion 10 of the generator.

Each frame plate 16 and each yoke plate 18 could be a unitary memberbut, preferably, for convenience in manufacture and assembly, each isfabricated of a plurality of pieces. Because tremendous magnetic forcesact on body portion 10 of the generator when the latter is in operation,the pieces comprising the frame plates and yoke plates are shaped andarranged so as to be interlocked when secured together. Thus, as FIG. 2shows, each frame plate 16 preferably comprises two rectangular endpieces 32 and two abutting side pieces 34. Each yoke plate 18 preferablycomprises two C-shaped end pieces 36 and four wedge shaped side pieces38.

The pieces comprising each yoke plate 18 are spaced apart from eachother and define a set of six radiating gaps which communicate betweencentral aperture 22 and two opposite exterior edges of the yoke plate.Each of the four gaps designated by the numeral 40 is adapted toaccommodate an electrode chute, hereinafter described, and each of thetwo gaps designated by the numeral 42 is adapted to accommodate gassupply means and other members, hereinafter described. As will beunderstood, the sides of the gaps 40 and 42 in each individual yokeplate 18 are closed by two adajacent frames plates 16 when body portion10 is assembled. It is to be further understood that while `the angulararrangement of the set of four gaps 40 in the yoke plate 18 shown inFIG. 2 is typical, the angular arrangement of the four gaps 40 in eachyoke plate differs, as comparison of FIGS. 6 and 8 make clear. Thispermits the set of electrode chutes accommodated by each yoke plate 18to enter body portion 10 at a different angle with respect to a plane ofsymmetry 41, shown in FIGS. 6 and 7, in which the axis of passageway 24lies.

Means are provided to secure the frame plates and the yoke plates andtheir constituent pieces together in proper alignment and to preventtheir displacement. As FIGS. 2 and 3 show, the pieces comprising eachframe plate 16 are provided with dowel holes 44 which extend 'completelytherethrough and are adapted to accommodate dowels or members 46. Thepieces comprising each yoke plate 18 are provided with registering dowelholes 48 which extend part way into the opposite faces thereof and areadapted to accommodate the ends of the dowels 46.

During assembly of body portion 10, the pieces comprising the lowestframe plate 16 are arranged on base member 12 of the generator and afirst set of dowels 46 are placed in the dowel holes 44. Then, thepieces comprising the lowest adjacent yoke plate 18 are placed on thelowest frame plate 16 so that the dowel holes 48 in the underside of theyoke plate receive the appropriate dowels 46. Another set of dowels 46are then placed in the dowel holes 48 in the upper side of the lowestyoke plate 18 and the pieces comprising the next adjacent frame plate 16are put in place on the yoke plate. This st-acking procedure is repeateduntil body portion 10 is completed. It is to be noted that each sidepiece 34 of a frame plate 16 is doweled to the two end pieces 36 and totwo of the side pieces 38 of its adjacent yoke plate or plates 18. Thus,the constituent pieces 0f a yoke plate 18 are maintained in properposition with respect to each other. It is to be understood that theinner and outer edges of the frame plates and the yoke plates areprovided with threaded holes where necessary to -accommodate fasteningdevices such as bolts which are employed to secure various components tothe exterior and interior sides of body portion 10.

The generator magn'et coil FIGS. 1, 4, 5, 6 and 8 show magnet coil 26which is the magnetic fiux producing means for the generator. Magnetcoil 26 is mechanically supported by base member 12 and by body portion1f) and is arranged within passageway 24 in the body portion so as tosurround the magnet poles 30. Disposition of magnet coil 26 within steelbody portion 10 reduces the reluctance of the magnetic circuit andconcentrates the magnetic field in the narrow space in passageway 24between the magnet poles 3f). For convenience, magnet coil 26 ispreferably fabricated of a number of smaller coil units 50 which areunderstood to be electrically interconnected, preferably in series. Inthe embodiment shown, magnet ycoil 26 cornprises eight substantiallyrectangular coil units 50 which are insulated from each other byinsulating means 51, as FIG. 6 shows, and each coil unit comprises aplurality of insulated conductors 52, shown in FIG. 6. Each conductor 52is provided with a cooling passage 56 to accommodate the flow of acooling fluid such as water for reducing the operating temperature ofmagnet coil 26. The coil units 5f) are all of the same thickness but, asFIGS. 5, 6 and 8 show, differ in width and are disposed in staggeredrelationship in order to adapt to the shape of tapered passageway 24 andto afford clearance for slanted electrode chutes, hereinafter described,which extend into the passageway. FIG. 6 shows that the edge of eachcoil unit 50 facing a fiow channel, hereinafter described, in passageway24 is provided with protective or shielding means, such as a fiuidcooled metal liner 53 having a cooling passage 54 therein, to protectthe coil unit from damage due to intense heat radiation which may leakpast the other components that are arranged between magnet coil 26 andthe flow channel in passageway 24. As FIGS. 1 and 4 make clear, the endsof the coil units 50 are bent outwardly away from the center line ofbody portion 1f) of the generator to afford clearance at each end ofpassageway 24; the lower ends of the coil units being maintained in thisposition by base 12 and the upper ends by spreader means 60.

The weight of magnet coil 26 is principally supported directly on basemember 12 but, as FIGS. 5, 6 and 8 show, blocking or supporting meansare provided, preferably at each frame plate 16, to rigidly secure coilunits 51 against displacement within passageway 24 of body portion 10.Preferably, the blocking or supporting means are frabricated ofnonmagnetic material so as not to interfere with or adversely affect thedesired magnetic circuit of the generator. FIGS. 5 and 8 show that theblocking or supporting means at each frame plate 16 comprise a member 62which is located in passageway 24 between the inner edge of end piece 32of the frame .plate and the outer side of magnet coil 26. FIGS. 5, 6 and8 show that the blocking or supporting means at each frame plate 16further comprise a member 64 which is located in passageway 24 betweenthe inner side of magnet coil 26 and the edge of side piece 34 of theframe plate. Because the blocking members 62 are relatively remote fromflow channel 28 and are not exposed to extremely high temperatures, itis preferable to fabricate them of low cost, nonmagnetic insulatingmaterial such as wood, Bakelite or the like. Because the blockingmembers 64 are relatively close to flow channel 28 and are exposed toextremely high temperatures, it is preferable to fabricate them ofnonmagnetic heat resistant material such as aluminum or stainless steel.

FIG. 3 shows that each blocking member 62 is secured in position byhaving its edge sandwiched between the pair of yoke plates 18 adjacenteach frame plate 16. It is to be further understood, as shown in FIG. 6,that each blocking member 64 is similarly secured in position by havinga portion of its edge sandwiched between a pair of yoke plates 18adjacent each frame plate 16.

As FIG. 4 shows, magnet coil 26 is provided with means such as theconductors 66 which adapt it for connection to a source 68 of electricalpower, such as a D.C. generator or the like. It may be assumed, forexample, that current ow through magnet coil 26 is in such a directionthat a magnetic field is provided transversely through passageway 24 inthe direction of the arrow 70 shown in FIGS. 4, 6, 7 and 8.

Gas supply means for flow channel As FIGS. l, 4, 5, 6, 7, 8 and 9 show,passageway 24 in body portion of the generator is adapted to accommodatemeans, hereinafter described, which cooperate to define heat resistant,thermally insulated, pressurized ow channel 28, hereinbefore referredto, through which hot, electrically gases ow.

The means for supplying such gases to flow channel 28 comprises acyclone furnace 72, shown in FIG. 4, which is located below base 12 ofthe generator. Cyclone furnace 72 has a fuel inlet 74, a combustion airinlet 76, and a gas outlet 78. Fuel inlet "I4 is adapted for connectionto a source 80 of fuel such as crushed coal or the like; crushed coalbeing preferred because it supports the high temperatures necessary, isreadily available, is relatively economical, and naturally containspotassium compounds which are extractable from the ash thereof forsubsequent use as seeding materials in operation of the generator.Combustion air inlet 76 is adapted for connection to a source 82 ofpressurized air, such as an air compressor which is understood to bepart of the overall plant. Gas outlet 78 is adapted for connection tothe wider end of a water cooled nozzle 84, shown in FIGS. 4 and 5, whichhas its narrower end connected to the narrow inlet end of flow channel28. Nozzle 84 is provided with an inlet port 86 through which seedingmaterials, such as the potassium com-pounds hereinbefore referred to,are introduced into the hot gas stream to render it `sufficientlyionized to produce the desired effect. The fuel and air are burnedtogether in cyclone furnace 72 to produce combustion gases which have atemperature in excess of 5050 F., and which, after passing throughnozzle 84, enter flow channel 28 at a subsonic velocity of about 800meters -per second. It is preferred that ow channel 28 be tapered Iso asto maintain the gases at substantially constant velocity therethrough.Furthermore, it is preferred that flow channel 28 have a rectangular,nearly square, cross sectional configuration to minimize the surfacearea thereof and thus reduce heat losses.

Flow channel institution means As FIGS. 4, 6, 7, 8 and 9 show, twoopposite sides of flow channel 28 are defined by insulating means whichare adapted to confine hot gases within the flow channel and toelectrically insulate between the electrode means, hereinafterdescribed, which substantially define the other two opposite sides ofthe flow channel. The aforesaid insulating means are further adapted toinhibit heat loss from flow channel 28. In keeping with the modularconstruction of the generator, the insulating means take the form of aplurality of individually replaceable modular insulating blocks ormembers 88 which are arranged in two rows along the face of each pole39. FIGS. 4 and 7 show that each block 88 is as long as the distancebetween the center lines of two successive frame plates 16 of bodyportion 19. If preferred, however, some other modular length could beemployed. FIGS. 6 and 8 show that each block 88 is approximatelyone-half as wide as flow channel 28, i.e., slightly wider than the inneror narrow end of one of the side pieces 38 of its associated yoke plate18. The blocks 88 are adapted to withstand prolonged exposure to theextremely high temperature, high velocity gases in flow channel 28.Thus, the blocks 88 are fabricated of heat resistant, electricalinsulating material such as magnesium oxide, thorium oxide, berylliumoxide or the like. Fully oxidized materials are preferred 'so thatfurther oxidation and attendant decomposition do not occur when theblocks are exposed to the -hot oxidizing atmosphere in ow channel 28.While the aforesaid materials have good resistance to mechanicalbreakdown at the high temperatures involved, they tend to becomeelectrically conductive at such temperatures. Accordingly, it isdesirable both to cool the blocks 88 and to prevent their direct contactwith the hot gases in ilow channel 28 and means are provided for thesepurposes.

Thus, as FIGS. 6, 7 and 9 show, each block 88 is pro vided with aplurality of passages 90 and each passage communicates with ow channel28 through a plurality of apertures or louvers @2 which are provided inthe face of each block. The passages 90 and the louvers 92 in each block88 are adapted to accommodate the flow of pressuried electricallynonconductive gas, such as cornpressed air or flue gas, which entersflow channel 28 through the louvers to provide a lilm or layer of gasalong the surface of the block facing the flow channel. This lm of gasprevents the hot electrically conductive gases in flow channel 28 fromdirectly contacting the surface of a block 88 and in addition tends tocool the block. Thus, the block 88 retains its normal electricalinsulating properties and is not directly exposed to the destructiveaction of the hot, high velocity gases in flow channel 28. If air is theelectrically nonconductive gas employed, such air entering tiow channel28 in the foregoing manner subsequently serves as secondary combustionair for the combustion process occurring therein.

As FIGS. 6, 8 and 9 show, each block 88 is provided on the rear sidethereof along its innermost edge with a recess 94 which intersects witheach passage 90 in the block. Thus, when two blocks are mounted inpassage way 24 in body. portion 10 in side-by-side position with theirinnermost edges juxtaposed, the recesses 94 cooperate to dene a gasinlet port 96 for the passages 9@ in the two blocks. As FIGS. 6 and 8show, each gas inlet port 96 communicates with a gas supply channel 98which is defined by insulating members 108 disposed in a gap 42 in theyoke plate 18 with which the two blocks are associated.

As FIG. 8 shows, each gas supply channel 98 communicates with a gas ducthousing 182 which is supported on the exterior of body portion I0 of thegenerator. As FIG. 1 shows, two separate gas duct housings 162 areprovided on one exterior side of body portion 10 and it is to beunderstood that two similar housings are provided on the opposite sideof the body portion. Each gas duct housing 162 is adapted for Connectionto a source of pressurized nonconductive gas, such as an air compressor106 which is understood to be part of the power plant in which thegenerator is employed. Separate gas duct housings are preferred in theembodiment shown so that each may be suppiled with gas or air atdifferent pressures. However, it is to be understood that the twoseparate duct housings on a side could be formed as a unitary member andsupplied from the same source of gas or air.

In addition to the louvers 92 which cross the face of each block 88,each block is provided with a plurality of slots 108 which are disposedso as to run in the same direction as the axis of ow channel 28. Theslots 108 provide a serrated surface on each block 88 and tend to reduceshort circuiting which might occur in flow channel 28 between electrodeson opposite sides of the flow channel.

As FIGS. 6 and 9 show, each block 88 is provided with means which adaptit to be secured in position. Such means take the form of two L-shapedslots 110 which are provided at the rear of each block and which areadapted to engage L-shaped metal brackets 112 which are rigidly securedas by welding to an electrical conductor 114, hereinafter described. Tosecure block 88 in position, it is first placed so that its slots 110register With the brackets 112 and then it is slid sideways so that ashoulder in each slot engages a leg of each bracket.

In addition to the insulating blocks 88 which line the aforesaid twoopposite sides of ow channel 28, similar insulating members are providedat intervals along the other two opposite sides of the flow channeldefined by the electrodes hereinafter described.

As FIGS. 6, 7, 8 and 9 show, an insulating member 113 is provided fordisposition between the exposed portions of each pair of electrodes ofthe same polarity to complete the aforesaid other two opposite sides ofow channel 28. It is to be understood that each insulating member 113 isfabricated of the same material as the insulating blocks 88 hereinbeforedescribed. Furthermore, each insulating member 113 is provided with aninternal passage 115 which intersects with a plurality of smallertransversely disposed passages 116 and the latter communicate withlouvers 117 which are provided in the face of each insulating member.When in place 1n passageway 24, each insulating member 113 mates withtwo associated insulating blocks 88 so that one of the 1nternal passages90 in each of the latter aligns with internal passage 115. Thus,pressurized gas from passage 90 1s supplied to the passage 115 in eachinulating member 113 and is expelled through the louvers 117 in thelatter to effect cooling of the latter.

As FIGS. 6 and 9 show, each insulating member 113 is provided at eachend with a slot 118 which is adapted to engage a bracket 119 which isrigidly attached as by Welding to the blocking member 64. As will beunderstood, during assembly of the generator each insulating member 113is placed in position subsequent to the positioning of blocks 88 withwhich it is associated but prior to the positioning of the electrodechutes 122.

Flow channel electrode means As FIGS. l, 6, 7, 8, 10, l1 and l2 show,the generator comprises electrode means for collecting electrical powergenerated by the hot electrically conductive gases as they move throughthe magnetic field in flow channel 28. Rather than provide onecontinuous electrode along each of the two opposite sides of flowchannel 28, it is preferred to provide a plurality of individualelectrodes 124, hereinafter described, which are arranged in two rows oneach of the two opposite sides of the oW channel. Provision of aplurality of electrodes and division of each into several distinctmasses, as hereinafter described, tends to reduce eddy currents in theelectrodes and also tends to reduce Hall effects in ilow channel 28. Theelectrode means comprise a plurality of substantially identicalelectrode units 120, such as that shown in FIG. 8, which are arranged intwo rows on two opposite sides of body portion 10 and which aremechanically supported thereby. As will be understood, each yoke plate18 has a set of four complete electrode units associated therewith in aradial arrangement.

The generator disclosed herein is adapted to produce D.C. electricalpower and, as FIG. 10 makes clear, the electrodes 124 along one side ofllow channel 28 are understood to be electrically negative and thosealong the other side are electrically positive. As FIGS. 6, 7, 8, 10 andl2 show, each electrode unit 120 comprises an electrode chute or box 122which is disposed in a gap 49 in a yoke plate 18. One end of eachelectrode chute 122 extends outside of body portion 10 of the generatorand the other end projects into passageway 24 between one side of magnetcoil 26 and ow channel 28. Each electrode chute 122 is adapted to haveelectrically conductive consumable material in particulate form, such ascrushed coal or the like, supplied thereto, compacted therein, andforced therethrough to provide a consumable electrode 124 having anexposed portion which confronts a side of flow channel 28. Preferably,seeding material in the form of potassium compounds is mixed with thecrushed coal which is supplied to the electrode chutes 122. Due to theintense heat in flow channel 28, the compacted coal near the inner endof each electrode chute 122 is converted to coke. As FIGS. 6, 7 and 8make clear, the exposed portions of the consumable electrodes 124 whichare arranged in two rows along two opposite sides of ow channel 28substantially define wall surfaces which are ablatable and are thus ableto withstand prolonged exposure to the hot, high velocity gases in theflow channel. For purposes of discussion herein, the term ablatable isused to describe the tendency of the material forming a consumableelectrode to burn, melt, evaporate, sublimate, erode away, or otherwisebe consumed when exposed to the high velocity ow of extremely hot gasesin llow channel 28. Each electrode chute 122 is fabricated ofabrasive-resistant, nonmagnetic material such as stainless steel or thelike. In order to insure that the crushed coal which is forcedtherethrough is rmly compacted, each electrode chute 122 is tapered and,in addition, is provided on the interior thereof with two dividers orwalls 130, shown in FIGS. 7, l1 and l2. The dividers also cause theextruded end of each consumable electrode 124 to be divided into threedistinct masses. Such division of the electrode surfaces results in areduction in eddy currents in the electrode surfaces.

Since it is desired that `flow channel 28 be tapered, it is necessarythat the exposed portions of the consumable electrodes 124, which arearranged along Iand define two sides thereof, vary in surface -area Iinorder to afford a fairly complete ablatable wall surface at allpositions along the ow channel. Accordingly, each set of four electrodechutes 122 associated Iwith a particular yoke plate 18 has a differentangular disposition with respect to plane of symmetry 41, as comparisonof FIGS. 6 and 8 makes clear. Furthermore, -the inner end of eachelectrode chute 122 terminates in a plane which -is substantiallyparallel to the boundary edge of one side of ow channel 28. Thisarrangement results in the necessary amount of electrode surface areabeing exposed at various electrode positions.

As FIGS. l, 6, 7 and 8 show, each electrode chute 122 is provided withmeans for making an electrical counection thereto and such rneans takethe form of an electrical conductor 114 which lies alongside theelectrode chute in .gap 40, extends across the -face of the adjacentmagnet pole 3u (i.e., across the narrower end of one side piece 38 ofthe associated yoke plate 18), and is led out through gap 42 in theassociated yoke plate 18. As FIG. 8 shows, one end of electricalconductor 114 is connected to an electrical terminal 131 by means of -aconductor 133. The other end of electrical conductor -114 is itselfadapted to serve as an electrical terminal. With the foregoingarrangement, it is possible to make a direct electrical connection to aconsumable electrode 124 in its electrode chute 122 directly throughelectrical terminal 131. If preferred, however, an electrical connectioncan be made to -t-he aforesaid other end of electrical conductor 114.With this latter arrangement, current iiows through electrical conductor114 in a direction opposite to th-at of the current flow in the gases inflow channel 28. This provides a compensating magnetic field aroundelectrical conductor 114 which cancels out or compensates for theeffects of variations in load currents on the excitation of thegenerator.

As FIGS. 6, 7 and 8 show, each electrode chute 122 and its associatedelectrical conductor 114 is provided with insulating means, such as theheat resistant insulating members 128 which prevent them from makingelectrical contact with their associated yoke plate 18.

Each electrical conductor 114 is provided with a passage 135 therein foraccommodating the flow of a cooling fluid such 'as water or othersuitable liquids or gases and connections 137, therefor shown in FIG. 8,are provided on each conductor.

As will Ibe understood, the electrodes 124 of the generator could bedirectly connected to a load to supply D.C. power thereto. However, itmay be desirable to convert D.C. power to A C. power before supplying itto a load and such an arrangement is shown in FIG. 10. To reduce Halleffects which may occur along the length of the generator, it ispreferable to connect each pair of electrodes 124 of opposite polarityin each set to individual inverter units 139 and to then connect theindividual inverter units to Ia common load device 141, as shown in FIG.10.

As FIGS. 6, 7 and 8 show, an insulating member 144 is located behindeach pair of electrode chutes 122 to afford further thermal insulationfor flow channel 28 and to serve as an inlet for a cooling gas such asyair which is directed against the rear of each pair of electrodechutes. Each insulating member 144, which is preferably fabricated ofthe same material yas the blocks 88 and the insulating members 132hereinbefore described, is provided with an internal passage 146 whichcommunicates with a plurality of slots 148i. The internal passage 146 inmember 144 is adapted for connection to a gas inlet 150 which extendsbetween the two adjacent center coil units 50 of magnet coil 26 andthrough a hole 152 in yoke plate 18 with which the two electrode chutes122 are associated. As FIG. 1 shows, pressurized gas from a source 154such as an air compressor located exterior of the generator is suppliedto gas inlet 150' in hole 152 and yafter passing through passage 146 ininsulating member 144 and slots 148, enters flow channel 28.

The electrode chutes 1122 and the consumable electrodes 124 therein, theinsulating members 132, the insulating members 144, the blocking members64 and the jackets 54 cooperate to insulate magnet coil 26 from exposureto the heat in flow channel 28 and inhibit heat loss from the flowchannel.

Electrode feeder means Means lfor supplying crushed coal to theelectrode chutes 122 are shown in FIGS. 1, 8, 11, 12 and 13. Since eachelectrode chute 122 and the consumable electrode 124 therein areelectrically conductive, it is necessary to -rnake provision toelectrically insulate them from the other apparatus making up theassoci-ated electrode unit 120, hereinafter described, which isassociated therewith and from the common supply of crushed coal. AsFIGS. 8, 11 and 12 show, the exterior end of each electrode chute 122 isadapted for connection to a feeder uni-t 156 which is rigidly mounted onthe outside of a body portion of the generator. It is to be understoodthat all the feeder units 156 are identical and are individuallyremovable. FIGS. 1 and 12 make clear that the feeder funits 156 arealigned in two rows on two opposi-te sides of the exterior of `bodyportion 16 and that each row is enclosed -by a coal chute or covermember 158 which is attached to body portion 111 and fabricated ofelectrical insulating material such as fiber glass or the like. As FIG.1 shows, each coal chute 158 is provided at its uppermost end with anaperture 160 which is adapted for connection to a source of crushedcoal.

Each feeder unit 156 comprises a pan member 162 and a cover member 164which are fabricated of insulating material such as fiberglass and arerigidly secured together to provide a chamber 166. Chamber 166 containstwo sprocket wheels 168 and 171i which drive a coal transfer chain 172which has a plurality of coal moving vanes 174 thereon. The cover member164 of feeder unit 156 is provided with a coal inlet port 176 over whicha coal input unit 178, best seen in FIGS. 8, l2 and 13, is lo cated.Input unit 178 comprises a nonconductive housing 188 having acylindrical chamber 182 therein which is provided with an inlet opening184 and an outlet opening 186 which register with coal inlet port 176 ininput unit 178. A coal hopper 188, fabricated of nonconductive materialsuch as ber glass, is secured to housing of input unit 178 over inletopening 184. Input unit 178 is provided with an electric mot-or fordriving a shaft 192 to which a bladed electrically nonconductive starwheel 194 located in cylindrical chamber 182 is rigidly attached.Nonconductive housing 180 of input unit 17S and its nonconductive starwheel 1% serve as an electrical insulating barrier or means ofseparation between the crushed coal in coal chute 158 and the crushedcoal in feeder unit 156. In this way, the consumable electrode 124 ineach electrode chute 122 is electrically isolated from the common supplyof crushed coal to prevent electrode short circuiting. As FIG. 12 shows,shaft 192 is also provided with a bevel gear 196 which drives anotherbevel gear 198 on a shaft 200 which drives sprocket Wheel 168 in chamber166 of feeder unit 156.

Pan member 162 of feeder unit 156 is provided on its exterior side withan integrally formed compacting cylinder 202 which has a steel cylinderlining 204 therein. Compacting cylinder 282 is in axial alignment withits associated electrode chute 122. Cylinder lining 204 has an opening206 which registers with a coal outlet port 208 in pan member 162.Cylinder lining 204 accommodates a coal packing piston 210, preferablyfabricated of steel, which is connected by an insulated connecting rodlinkage 212 to the interior driving mechanism of a driving unit 214.Driving unit 214 is provided with a drive motor 216 for driving thepiston slowly during its forward stroke when it is forcing ground coalinto and through electrode box 122. Driving unit 214 also is providedwith a clutch mechanism 218 for effecting disengagement of drive motor216 during the return stroke of piston 210. Driving unit 214 is furtherprovided with another motor 220 for effecting a quick return stroke ofpiston 210 while drive motor 216 is disengaged. The motors 190, 216, and228 and clutch mechanism 218 are understood to be in normally olf orinoperative conditions.

In operation, crushed coal is supplied to the coal chutes 158 and entershopper 188 of each feeder unit 156. The rotating star wheel 194 movesthe coal `from the hopper 156 through the chamber 132 into chamber 166of feeder unit 156. The vanes 174 on transformer chain 172, which isdriven by motor 19t), move the coal through chamber 166 from inlet port176 to outlet port 208 where it is ready to enter compacting cylinder282. When piston 218 is in the return position, the coal enterscompacting cylinder 202 and is gradually forced by the piston intoelectrode chute 122.

Due to the fact that the pressure within flow channel 28 in thegenerator is several times above atmospheric pressure, means must beprovided to prevent the electrode material in each electrode chute 122from being blown back up. Furthermore, it is desirable that the gasesformed as each electrode 124 cokes be forced from each electrode chute122 into flow channel 28 for combustion therein. Accordingly, it is tobe noted that a gastight path exists from the cylindrical chamber 182 ofeach input unit 178, through chamber 166 in feeder unit 156, throughcompacting cylinder 202, and through electrode chute 122. A vent tube222, shown in FIGS. 8 and 13, is understood to communicate betweencylindrical chamber 182 of input unit 178 and air inlet 150 forinsulating member 144 to insure that no pressure differential existsbetween chamber 182 and fiow channel 28.

During operation of the generator, the coked portion of each consumableelectrode 124 extending from the inner end of its respective electrodechute 122 burns, melts, ablates and erodes away at an average rate, forexample, of about one inch per minute but variations occur. If theconsumable electrodes 122 burn too short, the intense heat in flowchannel 28 can damage the electrode chutes 122 and other componentsalong the sides of the flow channel. Furthermore, the voltage across apair of oppositely disposed electrodes in an MHD generator depends,other factors being constant, on the distance between such electrodes.More particularly, increasing the distance between opposed electrodesincreases the voltage thereacross and decreasing the distance decreasesthe voltage. Accordingly, the means for supplying coal to each electrodechute 122 are adapted to operate when necessary to insure that theproper amount of consumable electrode projects from the electrode chute.

Means are provided to control and regulate the coal feed to eachelectrode chute 122. Thus, as FIGS. 8 and 12 show, the motors 190, 216and 220 and clutch mechanism 218 on each coal feed unit 120 areconnected to a control unit 224 which regulates the operation thereof inaccordance with a control signal received from a condition responsivedevice 226 located within flow channel 2S. As FIGS. 6 and 8 show,condition responsive device 226, which for example is understood to be athermally responsive device such as a thermocouple, is preferablylocated behind the exposed portion of its associated consumableelectrode 122 so as to be subjected to variations in temperaturedepending upon the amount of consumable material extending from the endof its associated electrode chute 124. Thus, if an individual electrode122 burns too short, its associated thermocouple experiences an increasein temperature and effects, through control unit 224, operation ofmotors 190, 216 and 220 and clutch mechanism 218 for that particularelectrode and effects an increase in the amount of coal being suppliedto its associated electrode chute 122. Conversely, when the projectingportion of the consumable electrode is restored, the associatedthermocouple exeriences a decrease in temperature and effects stoppageof motors 190, 216, 220 and clutch mechanism 218 4and a reduction in theamount of coal being supplied to the electrode chute.

Operation The generator operates in the following manner. Magnet coil 26is energized from D.C. source 68 and a magnetic field is establishedtransversely through flow channel 28 in the direction of arrow 70.

Pressurized air from the air compressors 106 is supplied to the air ducthousings 102 and from thence through the air supply channel 98 to theinternal passages 90 in the insulating blocks 88. Some of the airsupplied to the passages 90 in the blocks 88 is expelled through thelouvers 92 in the blocks 88 to provide a film of air along the surfacesof the latter and some of the air from the passages 90 in the blocks 88is supplied to the internal passages 134 in the insulating members 132for expulsion through the louvers 138 to provide a film of air along thesurfaces of the latter insulating members.

Additional pressurized air from air compressor 154 is supplied throughthe air inlets 150 to the air passages 146 in the insulating members 144behind the electrodes 124 for expulsion through the slots 148 in theinsulating members 144 to cool the electrodes.

Pressurized preheated air from air compressor 82 and crushed coal fromsource 80 are supplied to cyclone furnace 72 wherein combustion occursand hot comhustion gases from the cyclone furnace pass through nozzle 84into flow channel 28 of the generator. Seeding material is introducedinto the hot combustion gases through inlet port 86 in nozzle 84.

As the hot seeded ionized combustion gases move at high velocity throughthe magnetic field in flow channel 28, D.C. electrical current isgenerated in the gas stream and an electrical potential is establishedbetween opposite pairs of consumable electrodes 124 which line the flowchannel. Thus, as regards each pair of electrodes, electrical currentflows from one consumable electrode 124, through its associatedelectrode chute 122, through the rconductor member 114 associated withthe latter, through inverter 139, through the conductor member 114associated with the other electrode chute 122 comprising a pair, andthrough that electrode chute 122 to its associated consumable electrode124. Inverted current from inverter 139 is then supplied to load 141.

As explained hereinbefore, the hot gases flowing through ow channel 28are prevented from making direct contact with the blocks S8, theinsulating members 132 and the insulating members 144 by the films ofair which are provided on the surfaces thereof which confront the flowchannel. In addition, the air thus introduced into flow channel 28serves as secondary combustion air for the hot gases in the flowchannel.

The hot gases moving through flow channel 28 do, however, act on theexposed portions of the consumable electrodes 124 and effect burning,ablation and erosion thereof. Consumption of the electrodes 124 in thismanner contributes somewhat to the supply of hot gases in flow channel28 and the secondary combustion air, referred to above, insures completecombustion.

As noted hereinbefore, the motors 190, 216, 220 and clutch mechanism 218of each electrode feeder unit 156 are normally deenergized. However, ifan individual electrode 122 burns too short, its associated thermocouple226 experiences an increase in temperature and effects operation ofmoto-rs 190, 216, 218 and 220 of that particular feeder unit 156. Thus,when motor is energized, crushed coal which is on hand in the coalchutes 158 and in hopper 188 of each feeder unit 156 is moved byinsulated star wheel 194 through insulated chamber 182 into chamber 166of feed unit 156. Energization of motor 190 also causes movement oftransfer chain 172 and the vanes 174 thereon move the crushed coalthrough chamber 166 from inlet port 176 to outlet port 208 where it isready to enter compacting cylinder 202. Thus, when clutch mechanism 218effects disengagement of drive motor 216 and after motor 220 effectsquick return of piston 210, the crushed coal enters compacting cylinder202. When clutch mechanism 218 effects disengagement of motor 220, drivemotor 216 effects slow movement of piston 210 and the crushed coal isforced from compacting cylinder 202 into its associated electrode chute122.

Having now particularly described and ascertained the nature of our saidinvention and the manner in which it is to be performed, we declare thatwhat we claim is:

1. In an MHD device, in combination, a magnetizable body having apassageway therethrough, a magnet coil disposed within said passagewayand energizable to provide a magnetic field transversely through saidpassageway, and means within said passageway for defining a flow channelfor hot electrically conductive gases, said means comprising insulatingmeans arranged to insulate said body from said gas and discreteconsumable electrode means arranged to insulate said coil from said gas.

2. In an MHD device, in combination, a magnetizable body having apassageway therethrough, a magnet coil disposed within said passagewayand energizable to provide a magnetic field transversely through saidpassageway, and means within said passageway for defining a flow channelfor hot electrically conductive gases and for insulating saidmagnctizable body and said magnet coil from said gases, said meanscomprising insulating means defining opposite sides of said ow channel,said means further comprising discrete consumable electrode meanssubstantially defining two other opposite sides of said ow channel andarranged between said iiow channel and said magnet coil.

3. In an MHD device, in combination, a magnetizable body having apassageway therethrough, a magnet coil disposed within said passagewayand having its conductors axially arranged along two opposite sides ofsaid passageway, said magnet coil being energizable to provide amagnetic field transve-rsely through said passageway, insulating meansdisposed within said passageway for defining two opposite walls of aflow channel for hot electrically conductive gases, said insulatingmeans arranged to thermally and electrically insulate said body fromsaid gases, and discrete consumable electrode means disposed within saidpassageway for defining two other opposite walls of said flow channel,said electrode means arranged to insulate the conductors of said magnetcoil from said gases.

4. In an MHD device, in combination, a magne-tizable body having apassageway therethrough, a magnet coil disposed within said passagewayand havin-g its conductors axial-ly arranged along two opposite sides ofsaid passa-geway, said magnet coil being energizale to provide amagnetic field transversely through said passageway, discrete consumableelectrode means disposed within -said passageway for defining twoopposite walls of a flow channel for hot electrically conductive gases,first insulaaing means disposed between said discrete electnode means`for completing said two opposite walls of said ow channel, saidelectrode means `and said irst insulating means adapted to insulate theconductors of said magnet coil from said hot gases, and secondinsulating means disposed within said passageway for defining two otheropposite walls of said 4fiow channel, said second insulating meansanranged to thermally and electrically insulate said body from .saidgases.

f5. In an MHD device, in combination, a magnetizable body having apassageway extending axially therethrough, said body having a pluralityof openings therein which are arranged in rows along two sides thereof,said openings communicating from the exterior of said body to saidpassageway, a magnet coil `disposed within said passageway and havingits conductors axially arranged along two opposite sides of saidpassageway, said magnet coil being energizable to provide a magneticteld transversely through said passageway, a consumable electrode memberextending through each of said openings in said body and extending intosaid passageway in Afront of fthe conductors of said magnet coil, saidelectrode members deining two `opposite sides of a flow channel for hotelectrica-lly conductive gases, and insulating means defining two otheropposite sides of said iiow channel.

6. In an MHD device, in combination, a magnetizable body having apassageway extending axially therethrough, said body having a pluralityof openings therein which are arranged in rows along two sides thereof,said openings communicating from the exterior of said body to saidpassageway, a magnet coil disposed Iwithin said passageway and havingits conductors axially arranged along two opposite sides of saidpassageway, said magnet coil being energizable to provide a magnetictield transversely through said passageway, consumable electrode meansdisposed Within said passageway lfor substantially defining two oppositewal-ls of a ow channel for hot electrically conductive gases, saidelectrode means adapted to insulate the conductors of said magnet coilfrom said hot gases, and air cooled insulating means comprising aplurality 'of individually replaceable modular insulating blocksdisposed within said passageway for defining two other opposite walls ofsaid fiow channel and for thermally and electrically insulating saidbody from said gases,

said air cooled insulating means adapted to be supplied with air fromsaid openings in said body.

l7. In an MHD device, in combination, a magnetizable body having apassageway extending axially therethrough, said body having a pluralityof electrode accommodating opening-s therein lwhich are arranged in rowsalong two sides thereof and which communicate from the exterior of saidbody to said passageway, said body also having a plurality of airopenings therein which are arranged in ro-ws along two sides thereof andwhich communicate from the exterior of said body to said passageway, amagnet coil disposed within said passageway and having 'its conductorsaxially arranged along two opposite sides of said passageway, saidmagnet coil being energizable to provide a magnetic field transverselythrough said passageway, a consumable electrode member extendingIthrou-gh each of said electrode accommodating openings in said body andextending into said passageway in front of the conduct-ors of saidmagnet coil, said electrode members substantially defining two oppositesides of a flow channel for holt electrically conductive gases, 'firstair insulating means disposed within said passageway and defining t-woother opposite sides of said flow channel, said air insulating meansadapted to be supplied with air from said air openings in said body,.and second 4air insulating means disposed between individual electrodemembers to complete said two opposite sides of said ow channel, saidsecond air insulating means adapted :to 'be supplied with air from saidfirst air insulating means.

8. In an M'HD device, in combination, a magnetizable body having apassageway extending axially therethrough, said body having a pluralityof openings therein -which are arranged in rows along two sides thereof,said openings communicating trom the exterior of said body to saidpassageway, a magnet coil disposed within said passageway and having itsconduct-ors axially arranged along two opposite sides of saidpassageway, Sadi magnet coil being energizable Ito provide a magneticfield transversely through said passageway, discrete electrode meansdisposed within said passageway for substantially deiining two oppositewa-lls of a liow channel for hot electrically conductive gases, saiddi-screte electrode means adapted to insulate the conductors of saidmagnet coil from said hot gases, uirst air cooled insulating meansdisposed within said passageway for defining two other opposite walls ofsaid flow channel and for thermally and electrically insulating saidbody -from said gases, said air cooled insulating means adapted to besupplied twith air from said openings in said body, and second aircooled insulating means disposed between said discrete electrode meansfor completing said two opposite walls of said tlow channel, said secondair cooled insulating means being adapted to be supplied with air fromsaid dirst air cooled insulating means.

References Cited by the Examiner UNITED STATES PATENTS 957,242 5/ 1910Noeggerath 3.10-11 2,193,434 3/ 1940 Sem 13--18 3,102,224 8/ 19613-Maeder A310-11 X 3,161,788 12/1964 Russell 3-10-11 3,161,807 1-2/1964Brogan 310-11 X FOREIGN PATENTS 841,613 6/ 1952 Germany.

1,093,472 11/1960 Germany.

OTHER REFERENCES Publication: Westinghouse Engineer, July 1960, by Waypp. 105, 106 and 107.

ORIS L. RADBR, Primary Examiner.

DAVID X, SDI-HEY, Examiner.

1. IN AN MHD DEVICE, IN COMBINATION, A MAGNETIZABLE BODY HAVING APASSAGEWAY THERETHROUGH, A MAGNET COIL DISPOSED WITHIN SAID PASSAGEWAYAND ENERGIZABLE TO PROVIDE A MAGNETIC FIELD TRANSVERSELY THROUGH SAIDPASSAGEWAY, AND MEANS WITHIN SAID PASSAGEWAY FOR DEFINING A FLOW CHANNELFOR HOT ELECTRICALLY CONDUCTIVE GASES, SAID MEANS COMPRISING INSULATINGMEANS ARRANGED TO INSULATE SAID BODY FROM SAID GAS AND DISCRETECONSUMABLE ELECTRODE MEANS ARRANGED TO INSULATE SAID COIL FROM SAID GAS.